This application claims priority of Taiwanese Application No. 091118458, filed on Aug. 15, 2002.
1. Field of the Invention
The invention relates to an image projector system, more particularly to an image projector system having a light source that includes at least four light emitting diode modules.
2. Description of the Related Art
As shown in FIG. 1, a conventional image projector system includes a light source 90, a light-modulating device 91 for modulating light generated by the light source 90, and a projector lens set 92 for projecting modulated light from the light-modulating device 91 onto a screen (not shown). The power of projected modulated light beams that contain image data must be sufficiently high so that bright and clear images can be shown on the screen. A high-voltage mercury lamp 900 is widely used as the light source 90 for generating a high-intensity light beam. As a side effect, high temperatures are generated that not only cause deterioration and shortening of the service life of ambient components, but also degrade the lamp terminals. When the lamp terminals are degraded, the input voltage might not be sufficient to start the lamp 900. As a result, frequent replacement of the expensive high-voltage mercury lamp 900 must be conducted.
Furthermore, since the output of the high-voltage mercury lamp 900 includes large amounts of ultraviolet and infrared light, a number of optical filters must be disposed in the optical path within the image projector system. However, the presence of the optical filters can on the one hand abate the power of light beams projected by the image projector system, and on the other hand still allow a small percentage of the ultraviolet and infrared light to pass therethrough. As ultraviolet light tends to damage optical components in the optical path by virtue of its high-powered photons, and as infrared light tends to degrade optical components by virtue of heat rendered thereby, the presence of both ultraviolet and infrared light can shorten the service life of components of the image projector system.
Moreover, as observed in the color spectrum visible to the human eyes, the optimum wavelength for green light should be 525 nanometers. However, in view of limitations in light spectrum inherent to the high-voltage mercury lamp 900, the wavelength of green light rendered by the lamp 900 is around 550 nanometers. Furthermore, in the analysis of light-sensitive effect of human eyes, it was found that the intensity of green light is closely related to that of a whole range of light being sensed by the human eye. In other words, when the wavelength of rendered green light deviates from the optimum value of 525 nanometers, the presentability and intensity of composite light will be adversely affected. Another drawback of the high-voltage mercury lamp 900 resides in that, when the lamp 900 is turned on, the three primary colors, i.e., red, green and blue, must be emitted simultaneously. The primary colors cannot be sequentially emitted in a series of clock intervals. Therefore, since the image projector system must apply the technique of simultaneous display of red, green and blue color components, use of a single-packaged liquid crystal modulator is not possible.
Moreover, the transitory duration during turning on or turning off of the high-voltage mercury lamp 900 may require several hundreds of milliseconds or even reach several seconds. Since persistence of vision for human eyes only takes {fraction (1/15)} second, cyclic turning on and turning off of the lamp 900 will be perceived as discontinuous image rendering. As such, during use of the conventional image projector system, the high-voltage mercury lamp 900 must always be turned on, and cannot be momentarily turned off for lowering the operating temperature.
On the other hand, light emitting diodes not only have the advantages of light beams with smaller divergent angles and a wider range of available wavelengths for light emission, but also allow selective emission of differently colored light. As such, light emitting diodes of different colors can take turns in being applied with strong current for lowering the operating temperature. The power conversion efficiency of red light emitting diodes made by more mature manufacturing technology can be as high as 55%, while those of yellow-green light emitting diodes can be 32%. In view of the foregoing, light emitting diodes are more ideal candidates to serve as a light source for image projector systems than high-voltage mercury lamps. The only concern is that, in general, a light emitting diode can only emit light having several lumens, far less than the requirement of over a thousand lumens by the conventional liquid crystal image projector system.
Therefore, the main object of the present invention is to provide a light source that includes at least four light emitting diode modules for use in an image projector system to overcome the aforesaid drawbacks associated with the prior art.
Another object of the present invention is to provide an image projector system that incorporates the aforesaid light source.
According to one aspect of the present invention, there is provided a light source for an image projector system. The light source comprises:
a rectangular housing formed with a light-transmissive output port and at least four light-transmissive input ports;
at least four light emitting diode modules, each of which is mounted externally of the housing adjacent to a respective one of the light-transmissive input ports, each of the light emitting diode modules generating a light beam output that is transmitted into the housing through the respective one of the light-transmissive input ports, the light beam output of each of the light emitting diode modules having a wavelength band within a range of from 400 to 700 nanometers, the wavelength bands of the light beam outputs of the light emitting diode modules being different from each other, wherein a center wavelength of the wavelength band of the light beam output of each of the light emitting diode modules is spaced apart from that of other ones of the light emitting diode modules by at least 20 nanometers; and
a mirror set mounted in the housing for directing the light beam outputs of the light emitting diode modules that are transmitted into the housing to pass through the light-transmissive output port.
According to another aspect of the present invention, there is provided an image projector system that includes a light source, a light-modulating device for modulating light generated by the light source, and a projector lens set for projecting modulated light from the light-modulating device onto a screen. The light source includes:
a rectangular housing formed with a light-transmissive output port and at least four light-transmissive input ports;
at least four light emitting diode modules, each of which is mounted externally of the housing adjacent to a respective one of the light-transmissive input ports, each of the light emitting diode modules generating a light beam output that is transmitted into the housing through the respective one of the light-transmissive input ports, the light beam output of each of the light emitting diode modules having a wavelength band within a range of from 400 to 700 nanometers, the wavelength bands of the light beam outputs of the light emitting diode modules being different from each other, wherein a center wavelength of the wavelength band of the light beam output of each of the light emitting diode modules is spaced apart from that of other ones of the light emitting diode modules by at least 20 nanometers;
the light beam output of one of the light emitting diode modules corresponding to a red color output, the light beam output of one of the light emitting diode modules corresponding to a green color output, the light beam output of one of the light emitting diode modules corresponding to a blue color output; and
a mirror set mounted in the housing for directing the light beam outputs of the light emitting diode modules that are transmitted into the housing to pass through the light-transmissive output port for processing by the light-modulating device.